1. Field of the Invention
This invention relates generally to mechanical end face seals and more particularly to end face seals of the contacting type which provide for cooling the seal rings to remove the heat that is caused by rotational friction.
2. Background Art
Non-contacting mechanical face seals of the gap type create a fluid gap between the seal faces at the interface so that the fluid between the faces acts as a lubricant. Thus, non-contacting seals do not create a tremendous amount of heat at the interface because of the reduced friction between the relatively rotating rings. Moreover, a small amount of fluid which escapes between the sealing faces tends to cool the rings by absorbing and removing any heat which does develop.
Contacting seals have increased rotational friction relative to non-contacting seals because contacting seals develop frictional heat at the interface between the relatively rotating sealing faces. Thus, contacting seal design must take into account the heat generated by the friction of the relatively rotating seal faces at the interface. Normally, heat removal from the seal interface area of a contacting seal is achieved by conductive cooling through dissipation of the heat into the seal ring mass and distribution of the heat to an area removed from the seal interface. The heat is then dissipated into the environment from the ring portions located away from the seal interface. The amount of heat which these devices can effectively dissipate into the environment is necessarily limited by the temperature and convective properties of the material which is around the seal interface.
Attempts to cool the rings of a dual mechanical face seal arrangement have included circulating a buffer fluid through the buffer chamber by means of an internal circulation means. Examples of this type of device are disclosed in U.S. Pat. No. 4,721,311, issued to Kakabaker and U.S. Pat. No. 5,217,234 issued to Hornsby. The buffer fluid in both these devices is circulated through the buffer chamber in order to cool at least one of the sealing rings ill each of the two seals which define the dual seal apparatus.
It has been found that use of the present invention provides additional cooling to the rings of a seal and can significantly reduce the temperature of at least the outboard seal of a dual mechanical face seal arrangement. Reducing the temperature of a seal provides for a more effective seal due to reduction in the seal rings of mechanical stress and of thermal taper and a corresponding reduction in leakage from between the faces of a contacting seal.